This relates generally to electronic devices, and, more particularly, to coating layers for infrared-transparent sensor windows in electronic devices.
Electronic devices such as laptop computers, cellular telephones, and other equipment are sometimes provided with light sensors. For example, cellular telephones may sometimes include infrared proximity sensors. An infrared proximity sensor may include a light-emitting diode that emits infrared light and may include a light detector that measures the infrared light after the infrared light has been reflected off of the head of a user or other external object. The amount of light that is detected by the light detector is indicative of whether external objects are in the vicinity of the light sensor.
Sensors such as proximity sensors may be mounted behind an inactive area of a display. The display may have a protective layer of clear glass that serves as a display cover layer. The underside of the display cover layer may be coated with a black ink layer to hide internal components from view by a user. Windows may be formed in the black ink layer to accommodate components. Some windows, such as windows for visible-light cameras, may be transparent at visible light wavelengths. Other windows, such as those associated with infrared proximity sensors, may be provided with an ink (sometimes referred to as infrared ink) that is transparent at infrared wavelengths. The infrared ink may be opaque at visible wavelengths so that the infrared ink has a dark appearance that matches the black ink layer.
Infrared ink windows that are suitably opaque at visible wavelengths to match the appearance of nearby black ink in the black ink layer may scatter more light than desired at infrared wavelengths. This can make it difficult or impossible to achieve desired levels of sensor performance.
It would therefore be desirable to be able to provide enhanced visible-light-blocking-and-infrared-light-transparent window coatings to accommodate components such as sensors in an electronic device.